One of several different types of filters can be assigned to a trace listener through the Filter property to provide a layer of screening beyond that provided by the TraceSwitch. The filter can be used to control the event types that are produced by the listener.

This class filters events based on the value of the EventType property. This property can be set by code or in a configuration file to specify the event type of messages that should be traced by the listener. The value of the property indicates the threshold at which to begin tracing. Event types at and above the specified level are traced. The ShouldTrace method, called by listeners to determine if an event should be traced, uses the value of the EventType property.

To set the event type at which to begin tracing, edit the configuration file that corresponds to the name of your application. Within this file, you can add a listener, set its filter type, and specify the event type to trace. The configuration file should be formatted as follows.